Brake system condition warning system and switch assembly therefor

ABSTRACT

A switch assembly having switch sections separately actuated by front and rear brake pressures, and connected in electric circuitry to warn when either system fails to pressurize. The circuitry includes the parking brake warning light and the vehicle stoplights.

United States Patent Inventor Harold V. Elliott Saginaw, Mich.

Appl, No. 28,239

Filed Apr. 17, 1970 Patented Dec. 28, 1971 Assignee General MotorsCorporation Detroit, Mich.

Continuation of application Ser. No. 587,887, Oct. 19, 1966, nowabandoned. This application Apr. 17, 1970, Ser. No. 28,239

BRAKE SYSTEM CONDITION WARNING SYSTEM AND SWITCH ASSEMBLY THEREFOR 5Claims, 3 Drawing Figs.

U.S. Cl 340/60, ZOO/81.4, 340/52 C, 340/69 Int. Cl B60q I/44, B60t 17/22[50] Field of Search 188/1 A, 151 A; 200/814, 81.5; 340/52, 59, 60, 66,69, 71,

[56] References Cited UNITED STATES PATENTS 2,332,301 10/1943 Cox 340/60UX 3,011,595 12/1961 Heiss et a1 340/52CX Primary Examiner-John W.Caldwell Assistant Examinerl(enneth N. Leimer Att0meysW. E. Finken andD. D. McGraw ABSTRACT: A switch assembly having switch sectionsseparately actuated by front and rear brake pressures, and connected inelectric circuitry to warn when either system fails to pressurize. Thecircuitry includes the parking brake warning light and the vehiclestoplights.

BRAKE SYSTEM CONDITION WARNING SYSTEM AND SWITCH ASSEMBLY THEREFOR Thisapplication is a continuation of application Ser. No. 587,887, filedOct. 19, 1966, and now abandoned.

The invention relates to a system for providing a warning of thepresence or absence of certain conditions in a brake system, and moreparticularly to such a warning system which is responsive to thepresence and absence of fluid pressures in separate fluid pressurecircuits of a brake system. The invention further relates to warningsystem which is also responsive to a brake system condition such as theapplication and release of a vehicle parking brake portion of an entirevehicle brake system. The invention also relates to a switch assemblyfor such a warning system, and especially a switch assembly which sensesthe presence and absence of pressures in separate brake pressurecircuits. The warning system includes first and second warning means,with the first warning means being stop lamps which indicate to personsprimarily rearwardly of the vehicle that the vehicle brakes are appliedor being applied. The second warning means in the warning system whenactuated indicates that one of the brake circuits has no pressuretherein when the service brake pedal is applied, and, when alsoconnected with the vehicle parking brake, indicates that the parkingbrake is applied. The warning system may be connected through thevehicle ignition switch.

In the drawing:

FIG. 1 is a schematic representation of a warning system embodying theinvention connected with a vehicle brake system, with the switchassembly which is responsive to fluid pressures being illustrated withparts broken away and in sectron.

FIG. 2 is a schematic representation of a modified warning systemembodying the invention.

FIG. 3 is a cross-sectional view with parts broken away of a modifiedpressure-sensing switch assembly.

The vehicle brake system shown in FIG. 1 includes a parking brake leverwhich is suitably connected to apply the parking brake when actuated bythe vehicle operator, a service brake lever 12 connected to actuate themaster cylinder 14, a first fluid pressure actuated brake circuit 16connected to brakes such as the front wheel brakes l8, and a secondfluid pressure actuated brake circuit 20 connected to brakes such as therear wheel brakes 22. Since the circuits l6 and 20 are separatelypressurized by the master cylinder 14, the master cylinder is of thedual master cylinder type.

A switch assembly 24 is provided as part of the warning system, as isthe nonnally open parking brake switch 26. When the parking brake lever10 is moved to apply the parking brake, switch 26 is closed. Thus thisswitch senses the presence and absence of the application of a brakesystem condition, which is the application or lack of application of theparking brake.

The switch assembly 24 has a housing upper recessed section 28 securedto a housing lower section 30. Terminal posts 32 and 34 are secured inthe housing upper section 28 and are electrically connected by suitablemeans such as the connector strip 36. Terminal post 38 is also mountedin the housing upper section 28 and has the inner end thereof providinga mounting and electrical connection to contact mounting spring 40. Post38 is connected to the center of spring 40 so that the spring hascantilever arms 42 and 44 extending therefrom. A'connector strip 46 isalso mounted in the switch assembly housing and provides a base forfirst contacts 48 and 50, respectively, of switches 52 and 54. Secondcontacts 56 and 58 are respectively mounted on the inner ends of posts32 and 34 and also respectively form parts of switches 52 and 54. Thirdcontacts 60 and 62 are respectively mounted on opposite ends of arms 42and 44 and are double headed in form and also respectively form parts ofswitches 52 and 54. Contacts 48, 56 and 60 of switch 52 are inalignment, with the spring force or arm 42 of spring 40 biasing contact60 into engagement with contact 48. Contacts 50, 58 and 62 of switch 54are similarly arranged, with contact 62 being biased into engagementwith contact 50 by the spring force of arm 44.

The switch assembly lower housing section 30 has chambers 64 and 66formed therein which are respectively fluid connected by conduits 68 and70 to their respective fluid pressure circuits l6 and 20. A piston 72 isprovided with a pressure cup 74 on one end and a plunger 76 on the otherend and is reciprocably mounted in chamber 64, being retained therein byretainer 78. Plunger 76 extends through retainer 78 and into engagementwith spring arm 42. A similar piston 80 with a cup 82 and a plunger 84is reciprocably received in chamber 66 and retained therein by retainer86. Plunger 84 engages spring arm 44. It can be seen that when fluidpressure is applied in chamber 64, for example, plunger 76 is movedupwardly against the biasing force of arm 42 and contact 60 is moved outof engagement with contact 48 and into engagement with contact 56.Similarly, when pressure is applied in chamber 66, plunger 84 is movedupwardly against the biasing force of arm 44 and moves contact 62 out ofengagement with contact 50 and into engagement with contact 58.

The warning system electrical circuit includes a source of electricalenergy schematically illustrated as a battery 88 connected throughelectrical lead 90 and ignition switch 92 to post 32 and thereforecontacts 56 and 58. Electrical lead 94 connects post 34, and thereforecontact 58, with one contact 96 of the parking brake switch 26. Theouter parking brake switch contact 98 is connected by electrical leadI00 to connector strip 46 and therefore to contacts 48 and 50.Electrical lead 102 connects with lead 100 and through a warning device,such as warning lamp 104, to ground. Electrical lead 106 connects post38, and therefore contacts 60 and 62, through spring 40, through awarning device, such as stop lamps 108, to ground.

In the brake system of FIG. 1, there are three brake conditions whichare sensed by the sensing means including the switch assembly 24 and theswitch 26. One condition is the presence or absence of fluid pressure incircuit 16. Another condition is the presence or absence of fluidpressure in circuit 20. A third condition is the application or releaseof the vehicle parking brake. When all systems are operating normally,with the ignition switch 92 closed, and all brake systems in thereleased condition, substantially no fluid pressures exist in circuits16 and 20 and brake switch 26 is open. The switches of the sensing meansare therefore in the positions shown in FIG. 1. If the vehicle servicebrakes are normally applied by depression of lever 12 and pressurizationof circuits l6 and 20 by master cylinder 14, both pistons 72 and 80 willrespond to these pressures and both plungers 76 and 84 will moveupwardly so that the third contacts 60 and 62 disengage the firstcontacts 48 and 50 and engage the second contacts 56 and 58,respectively. This will complete an electrical circuit to the stop lamps108, which operate as first warning means. Although electrical lead 94is energized, switch 26 is open and therefore the second warning meansprovided by the warning lamp 104 is not actuated. If, however, eithercircuit 16 or circuit 20 fails to have fluid pressurized therein, theassociated piston and plunger will not move and the associated thirdcontact will not be moved. Should a pressure failure occur in circuit16, for example, contact 60 will remain in engagement with contact 48.With circuit 20 pressurized, contact 62 will engage contact 58. If thepressure failure is in circuit 20, with circuit 16 being normallypressurized, the reverse will take place. In either instance, the firstwarning means 108 will be actuated through the sensing manes. However,since contact 60, for example, does not move, contact 48 will also beelectrically energized, as will leads 100 and 102 and the second warningmeans 104. Lamp 104 is positioned in the vehicle as to immediately bringto the attention of the vehicle operator the fact that one of the brakeconditions which should have been present upon brake actuation is infact absent, or vice versa. Since this signal occurred during theactuation of the vehicle service brakes, the operator is immediatelywarned that one of the service brake circuits has not been pressurized.

When a vehicle is parked with the parking brake applied, the ignitionswitch 92 is normally open. However, should the operator close theignition switch as, for example, when preparing to start the vehicle,without releasing the parking brake, the warning lamp 104 will beenergized through lead 90, connector strip 36, lead 94, lead 100 andlead 102. Since contacts 60 and 62 are respectively in engagement withcontacts 48 and 50, the stop lamps 108 will also be energized throughlead 100, spring 40, post 38, and lead 106. This arrangement will alsowarn persons outside and to the rear of the vehicle that at least aportion of the vehicle brake system is applied. The actuation of thestop lamps while the ignition switch is closed and the parking brakeapplied will also more clearly bring to the attention of other vehicleoperators the presence of the vehicle equipped with this warning system,and that vehicle is probably occupied so that some movement of thevehicle may shortly occur. The stop lamps will remain actuated if theoperator also depresses the service brake lever, assuming at least oneof the circuits l6 and to be normally pressurized thereby. Since theoperator will observe the actuation of warning lamp 104, he willrecognize that his parking brake is applied and will release it to openswitch 26. The warning lamp 104 and the stop lamps 108 will then bedeenergized, assuming the service brakes to be released.

The modified system schematically illustrated in FIG. 2 has the ignitionswitch 92 placed in lead 104 instead of lead 90. This permits the stoplamps 108 to be energized upon pressurization of either of the brakecircuits 16 or 20, or both, without the ignition switch being closed. Ifonly one of the brake circuits is pressurized, warning lamp 104 willalso be energized even though the ignition switch is open. However, whenthe parking brake is applied, with switch 26 therefore closed, warninglamp 104 will be actuated because of application of the parking brakeonly when the ignition switch 92 is closed. Thus the warning lamp 104will not be actuated during long periods of time while the vehicleparking brakes are applied and the ignition switch is open. It will,however, be immediately actuated whenever the service brakes are appliedand one of the circuits fails to generate pressure therein.

The modified switch assembly 124 shown in FIG. 3 is similar to switchassembly 24 of FIG. 1, except that a somewhat different arrangement isutilized to respond to pressures in chambers 64 and 66. In this instanceflexible diaphragms 172 and 180 respectively seal pressure chambers 64and 66 at the chamber upper ends and are respectively engaged byplungers 176 and 184. These plungers respectively engage spring arms 42and 44 and operate in the same manner as described above with regard toswitch assembly 24.

A brake condition warning system and a switch assembly for the systemhas been disclosed which will warn persons of the presence or absence ofseveral brake conditions. The brake condition warning system may beutilized without the parking brake switch portion of thecondition-sensing means, or with it. Considering a first brake conditionto be the presence of fluid pressure in circuit 16, a second brakecondition to be the presence of fluid pressure in circuit 20, and athird brake condition to be the application of the vehicle parkingbrake, the sensing means including the switch assembly 24 and the switch26 senses the presence and absence of each of these conditions. If, forexample, only the first condition occurs, the first warning means 108and the second warning means 104 will be actuated through the sensingmeans, If only the second brake system condition occurs, the first andsecond warning means will both be energized. If only the third brakesystem condition occurs, both the first and second warning means will beactuated. If the first and third brake system conditions are present andthe second brake system condition is absent, both the first and secondwarning means will be actuated through the sensing means. If the secondand third brake system conditions are present and the first brakecondition is absent, both the first and second warning means will beactuated through the sensing means. If the first and second brakeconditions are present and the third brake condition is absent, only thefirst warning means will be actuated. The above situations are allpredicated on the fact that the ignition switch 92 is closed, in thesystem of FIG. 1. When the ignition switch 92 is open in the system ofFIG. 1, neither of the warning means may be energized. However, when theignition switch 92 is open in the system of FIG. 2, the stop lamps 108and the warning lamp 104 are energized if the service brakes are appliedand only one of the first and second brake conditions is present. Whenboth the first and second brake conditions are present, only the stoplamps 108 will be energized. The first and second warning means will notbe energized due to the presence of only the third condition unlessignition switch 92 is closed.

What is claimed is:

l. A brake system condition warning system comprising:

first and second and third brake system condition sensors respectivelysensing the presence and absence of first and second and third brakesystem conditions,

first warning means actuated through at least one of said first andsecond sensors by the presence of at least one brake condition sensed byat least one of said first and second sensors,

and second warning means actuated through a series connection formedthrough said first and second sensors by the presence of one and theabsence of the other of said first and second brake conditions sensed bysaid first and second sensors,

said second warning means also being actuated through said third sensorby the presence of said third brake system condition irrespective ofsaid first and second brake system conditions.

2. The brake system condition warning system of claim 1,

said first brake system condition being the brake-actuatingpressurization of a first fluid pressure actuated brake system circuitsystem in the brake system,

said second brake system condition being the brake-actuatingpressurization of a second fluid pressure actuated brake circuit in thebrake system,

and said third brake system condition being the application of a parkingbrake.

3. The brake system condition warning system of claim 2, said first andsecond and third sensors respectively comprising first and second andthird switches, each of said first and second switches having first andsecond and third contacts and means biasing said third contact intoengagement with said first contact and pressure-responsive means fluidconnected with a fluid pressure actuated brake circuit and actuable uponpressurization of the associated fluid pressure actuated brake circuitto move said third contact from engagement with said first contact toengagement with said second contact,

said third switch being a normally open switch and having fourth andfifth contacts closed by application of a parking brake.

4. The brake system condition warning system of claim 3,

further comprising:

a source of electrical energy and means connecting said second andfourth contacts thereto,

means connecting said third contacts to said first warning means,

and means connecting said first and fifth contacts to said secondwarning means.

5. In a vehicle having first and second fluidly independent hydraulicbrake circuits and means for pressurizing each circuit to actuatevehicle brakes, a vehicle multiple hydraulic brake circuit conditionindicating system comprising a combination:

a hydraulic circuit condition sensing assembly for sensing hydraulicfluid pressure conditions of each of said hydraulic circuits, theconditions being sensed being the presence and absence of predetenninedhydraulic pressures in each of said hydraulic circuits when saidpressurizing means are actuated, said sensing assembly comprising foreach of said hydraulic circuits connected thereto:

a hydraulic pressure responsive displacement member, means biasing saiddisplacement member against hydraulic pressure in the hydraulic circuitconnected thereto and being overcome at a predetermined minimumhydraulic pressure in the hydraulic circuit connected thereto andpermitting displacement of said displacement member,

a switch having first and second and third electrical contacts inaligned relation, said first and third contacts being spaced apart andreceiving said second contact therebetween for displaceable movementbetween positions in which said second contact electrically engages saidfirst contact, said second contact is electrically disengaged from saidfirst and third contacts, and said second contact is electricallyengaged with said third contact,

said second contact being connected with said biasing means and beingbiased thereby into electrical engagement with said first contact, andbeing operatively connected to said displacement member to be moved outof electrical engagement with said first contact upon the displacementof said displacement member by the predetermined minimum pressure insaid hydraulic circuit connected thereto, and being thereafter movedinto electrical engagement with said third contact at a predeterminedhigher pressure in the hydraulic circuit connected thereto which causesfurther displacement of said displacement member against said biasingmeans,

said biasing means returning said second electrical contact fromelectrical engagement with said third contact to electrical engagementwith said first contact and returning said displacement member to itspredisplaced position upon the decrease of hydraulic pressure in thehydraulic circuit connected thereto below said predetermined minimumhydraulic pressure;

a vehicle brake having brake apply and release conditions independent ofsaid hydraulic circuit conditions and being indicated by anoperator-controlled switch which is open when the brake is released andis closed when the brake is applied;

said sensing assembly having each of said first contacts for each ofsaid hydraulic circuits electrically connected and each of said secondcontacts for each of said hydraulic circuits electrically connected andeach of said third contacts for each of said hydraulic circuitselectrically connected;

first and second electrically energizable indicators;

and a source of electrical energy having an electrical ground and anelectrical energy output, said output being electrically connected tosaid third contacts and through said operator-controlled switch andthrough said first electrically energizable indicator to electricalground;

said second electrically energizable indicator having said secondcontacts electrically connected therethrough to electrical ground;

said first contacts being electrically connected through said firstelectrically energizable indicator to electrical ground.

1. A brake system condition warning system comprising: first and secondand third brake system condition sensors respectively sensing thepresence and absence of first and second and third brake systemconditions, first warning means actuated through at least one of saidfirst and second sensors by the presence of at least one brake conditionsensed by at least one of said first and second sensors, and secondwarning means actuated through a series connection formed through saidfirst and second sensors by the presence of one and the absence of theother of said first and second brake conditions sensed by said first andsecond sensors, said second warning means also being actuated throughsaid third sensor by the presence of said third brake system conditionirrespective of said first and second brake system conditions.
 2. Thebrake system condition warning system of claim 1, said first brakesystem condition being the brake-actuating pressurization of a firstfluid pressure actuated brake system circuit system in the brake system,said second brake system condition being the brake-actuatingpressurization of a second fluid pressure actuated brake circuit in thebrake system, and said third brake system condition being theapplication of a parking brake.
 3. The brake system condition warningsystem of claim 2, said first and second and third sensors respectivelycomprising first and second and third switches, each of said first andsecond switches having first and second and third contacts and meansbiasing sAid third contact into engagement with said first contact andpressure-responsive means fluid connected with a fluid pressure actuatedbrake circuit and actuable upon pressurization of the associated fluidpressure actuated brake circuit to move said third contact fromengagement with said first contact to engagement with said secondcontact, said third switch being a normally open switch and havingfourth and fifth contacts closed by application of a parking brake. 4.The brake system condition warning system of claim 3, furthercomprising: a source of electrical energy and means connecting saidsecond and fourth contacts thereto, means connecting said third contactsto said first warning means, and means connecting said first and fifthcontacts to said second warning means.
 5. In a vehicle having first andsecond fluidly independent hydraulic brake circuits and means forpressurizing each circuit to actuate vehicle brakes, a vehicle multiplehydraulic brake circuit condition indicating system comprising incombination: a hydraulic circuit condition sensing assembly for sensinghydraulic fluid pressure conditions of each of said hydraulic circuits,the conditions being sensed being the presence and absence ofpredetermined hydraulic pressures in each of said hydraulic circuitswhen said pressurizing means are actuated, said sensing assemblycomprising for each of said hydraulic circuits connected thereto: ahydraulic pressure responsive displacement member, means biasing saiddisplacement member against hydraulic pressure in the hydraulic circuitconnected thereto and being overcome at a predetermined minimumhydraulic pressure in the hydraulic circuit connected thereto andpermitting displacement of said displacement member, a switch havingfirst and second and third electrical contacts in aligned relation, saidfirst and third contacts being spaced apart and receiving said secondcontact therebetween for displaceable movement between positions inwhich said second contact electrically engages said first contact, saidsecond contact is electrically disengaged from said first and thirdcontacts, and said second contact is electrically engaged with saidthird contact, said second contact being connected with said biasingmeans and being biased thereby into electrical engagement with saidfirst contact, and being operatively connected to said displacementmember to be moved out of electrical engagement with said first contactupon the displacement of said displacement member by the predeterminedminimum pressure in said hydraulic circuit connected thereto, and beingthereafter moved into electrical engagement with said third contact at apredetermined higher pressure in the hydraulic circuit connected theretowhich causes further displacement of said displacement member againstsaid biasing means, said biasing means returning said second electricalcontact from electrical engagement with said third contact to electricalengagement with said first contact and returning said displacementmember to its predisplaced position upon the decrease of hydraulicpressure in the hydraulic circuit connected thereto below saidpredetermined minimum hydraulic pressure; a vehicle brake having brakeapply and release conditions independent of said hydraulic circuitconditions and being indicated by an operator-controlled switch which isopen when the brake is released and is closed when the brake is applied;said sensing assembly having each of said first contacts for each ofsaid hydraulic circuits electrically connected and each of said secondcontacts for each of said hydraulic circuits electrically connected andeach of said third contacts for each of said hydraulic circuitselectrically connected; first and second electrically energizableindicators; and a source of electrical energy having an electricalground and an electrical energy output, said output being electricallyconnected to said third contacts and through sAid operator-controlledswitch and through said first electrically energizable indicator toelectrical ground; said second electrically energizable indicator havingsaid second contacts electrically connected therethrough to electricalground; said first contacts being electrically connected through saidfirst electrically energizable indicator to electrical ground.